1500 V N-channel in a full-pack isolated tab
The STMicroelectronics STFW4N150 is a 1500 V, 4 A N-channel PowerMESH MOSFET in a TO-3PF full-pack through-hole package. The 1500 V drain-source rating places it squarely in high-voltage offline applications — flyback converters, PFC stages, two-switch forward converters, and auxiliary power supplies where the primary-side rail runs off rectified mains.
7 Ohm Rds(on) — conduction loss budget
On-resistance is specified at 7 Ohm maximum with 10 V gate drive at 2 A drain current. That is a relatively high figure compared to low-voltage switching FETs, but at 1500 V the die is sized for voltage blocking, not low Rds(on). Conduction loss at 2 A is I²R = 28 W, which consumes nearly half the 63 W power dissipation budget at 25°C case temperature. Practical designs will run at lower duty cycles or lower average currents to stay inside the SOA.
That is modest — a standard gate driver IC or a simple resistor-capacitor drive network can charge the gate in a few hundred nanoseconds. The 50 nC Qg means the gate drive power at 100 kHz switching is Pgate = Qg × Vgs × fsw = 50 nC × 10 V × 100 kHz = 50 mW, easily handled by a small driver. The 1300 pF Ciss keeps the Miller plateau short, so switching losses in a resonant or quasi-resonant topology stay manageable.
The base product number is STFW4, which covers the family variants — confirm the exact suffix for your BOM line.